Choosing the right kind of pump for your garden fountain or pond is critically important for its proper functioning. If a wrong pump is chosen, it may damage the entire system and render it useless.
Pumps are measured in terms of gallons per hour (GPH) they circulate. This GPH capacity of a pump ranges anywhere between fifty GPH to several thousand GPH. The amount of GPH you need for you pump depends on the size of equipment that is using it. Bigger equipments need higher GPH ratings.
Most garden fountains uses pump that produce anywhere between 300 to 1200 gallons per hour. Small ponds uses pump that produce about 500 to 700 GPH.
Here's a simple way to decide the GPH ratings of your pump.
First measure the amount of water that is being held by the fountain or pond. This can be done by measuring the width, depth, and length of the water basin of your fountain or pond. If your water feature is a pond, measure the average depth, average width, and average length of your pond. Measure these numbers in feet. Now multiply these three numbers to determine its volume. Multiple the volume with 7.5 and you would get the average amount of gallons of water your pond holds. The reason we multiply the volume by 7.5 is because an average cubic foot of space holds about 7.5 gallons of water. If you final gallon amount of water is about 700, then a water pump with 500 GPH rating is adequate.
The reason we choose 500 gallons per hour pump for a 700 gallon pond is because we want to make sure that the entire volume of water is re-circulated every two hours. This one trick of making sure that the entire volume gets re-circulated ever two hours is the most important criteria when it comes to choosing a water pump. Since the pump that we chose has 500 gph rating, it would re-circulate 1000 gallons of water every two hours. This makes it perfectly suitable for a pond that has got 700 gallons of water. We could have chosen a 350 GPH pump to be accurate for this example; however, it is generally best to purchase a slightly larger pump to account for the loss of pressure and hose friction.
Another important aspect of choosing a pump is its energy efficiency. A garden fountain that has direct exposure to sun may be a perfect choice for a solar pump that has zero operational costs. Water-filtration is another important factor when choosing the pumps. A large pond has lot of debris and it is critically important to pick the pump that can filter solid debris.
